All About Java Syntax

All About Java Syntax

8 mins readComment
Esha
Esha Gupta
Associate Senior Executive
Updated on Mar 11, 2024 16:43 IST

Have you ever wondered how Java, one of the most popular programming languages, structures its code? Understanding Java syntax is key to this, encompassing a set of precise rules and conventions. From variables and data types to control structures and object-oriented concepts, Java's syntax forms the backbone of its clear and efficient code structure, guiding programmers in creating robust applications. Let's understand more!

Java syntax refers to the set of rules and conventions that define the structure of Java code. It governs how Java programs are written and dictates the way in which different elements of the language such as keywords, operators, data types, control structures, and other components are used and combined to form valid Java programs. Understanding Java syntax is essential for writing correct and efficient Java code.

Java Syntax Rules

Some of the key syntax rules in Java are as follows:

  • Case Sensitivity: Java is case-sensitive, which means that identifiers like variable names, class names, and method names are distinct in different cases. For example, myVariable, MyVariable, and MYVARIABLE are different identifiers.
  • Class Names: The first letter of class names should be in uppercase. If several words are used to form the name of the class, each inner word’s first letter should be in uppercase. Example: MyClass, MyVeryLongClassName
  • Method Names: Unlike class names, method names in Java should start with a lowercase letter. If the method name contains multiple words, then each inner word should start with an uppercase letter. Example: myMethodName, calculateTotalWidth
  • Program File Name: The name of the program file should exactly match the class name. When saving the file, you should use the class name and append .java to the end of the name (if the class is public).
  • public static void main(String[] args): This is the main method in which the program execution begins. Every Java application must have this method as its starting point.
  • Curly Braces: Blocks of code are defined using curly braces {}. The opening brace should be at the end of the line where the block begins, and the closing brace should be on its own line.
  • Semicolons: In Java, semicolons are used to terminate statements. It’s important to end most lines of code with a semicolon to indicate the end of a statement.
  • Variable Declarations: All variables must be declared before they can be used. The declaration typically includes the data type and the variable name, like int number;
  • Constants: The final keyword is used to declare constants in Java. Once a constant is declared, its value cannot be changed. Example: final double PI = 3.14159;
  • Commenting: Java supports single-line comments (//) and multi-line comments (/* ... */). Comments are ignored by the Java compiler and serve as notes for the programmer.
  • Import Statements: To use classes and interfaces that are part of other packages, your program must include an import statement for that package. Example: import java.util.Scanner;
  • Package Declarations: If a file contains a package statement, it must be the first line in the file, excluding comments.
  • Object and Variable Initialization: Objects and variables should be properly initialized before they are used.
  • String Literals: String literals in Java are enclosed in double quotes. Example: "This is a string"
  • Java Keywords: Java keywords, like public, static, class, etc., are reserved words and should not be used as variable names or identifiers.

Now, let's see some major Java concepts with a brief explanation and basic syntax examples.

Concept

Description

Syntax Example

Variables

Storing data values.

int number = 5;

Data Types

Types of data (e.g., int, double, char, String).

int myNum = 5;
double rate = 3.14;
String name = "Java";

Operators

Performing operations on variables and values.

int sum = a + b; // Arithmetic
boolean isTrue = (a == b); // Logical

Control Structures

Directing the flow of the program.

if (condition) {
    // code
} else {
    // code
}
for (int i = 0; i < 5; i++) {
    // code
}

Arrays

Storing multiple values in a single variable.

int[] myArray = new int[5];

Methods

Blocks of code designed to perform tasks.

public int multiply(int a, int b) {
    return a * b;
}

Classes and Objects

Templates for objects and creating instances.

public class MyClass {
    // fields, methods, constructors
}
MyClass myObj = new MyClass();

Inheritance

Deriving new classes from existing ones.

class MyChildClass extends MyParentClass {
    // additional fields, methods
}

Interfaces

Implementing methods across different classes.

interface MyInterface {
    // abstract methods
}
class MyClass implements MyInterface {
    // implementation of abstract methods
}

Exception Handling

Managing errors and exceptions in code.

try {
    // code that may throw an exception
} catch (Exception e) {
    // code to handle the exception
}

Generics

Enabling classes and methods to operate on types.

class MyGenericClass<T> {
    // using the type parameter T
}

Abstract Classes

Classes that cannot be instantiated.

abstract class MyAbstractClass {
    // abstract methods
}

Polymorphism

Allowing methods to perform differently based on the object.

@Override
public void display() {
    // overridden method
}

Encapsulation

Restricting direct access to some of an object's components.

private int data;

Static Keyword

Denoting class-level properties and behaviours.

static int value = 5;
public static void myStaticMethod() {
    // static method code
}

Final Keyword

Creating constants and preventing inheritance.

final int MAX = 100;
final class MyFinalClass {
    // class code
}

Concurrency

Handling multiple processes or threads.

Runnable runnable = () -> {
    // thread task
};
Thread myThread = new Thread(runnable);
myThread.start();

Java API & Libraries

Utilizing Java's built-in libraries and functions.

List<String> list = new ArrayList<>();
list.add("Hello");

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Basic Terminologies in Java

The table below covers the basic terminologies that are essential to understanding Java and its ecosystem. Each term represents a fundamental concept in Java programming and software development with this language.

Term

Definition

Class

A blueprint for creating objects containing methods, variables, and more.

Object

An instance of a class; it has state and behavior as defined by its class.

Method

A block of code within a class that performs a specific task.

Variable

A container for storing data values.

Constructor

A special method used to initialize new objects of a class.

Inheritance

The mechanism by which one class can inherit the features of another class.

Interface

An abstract type used to specify a behavior that classes must implement.

Abstract Class

A class that cannot be instantiated and is often used as a base class.

Polymorphism

The ability of a variable, function, or object to take on multiple forms.

Encapsulation

The bundling of data and methods that operate on the data within one unit, like a class.

Package

A namespace for organizing classes and interfaces in a logical manner.

Array

A container object that holds a fixed number of values of a single type.

Exception

An event that disrupts the normal flow of the program's instructions.

Loop

A control structure that repeatedly executes a block of code as long as a particular condition is true.

Conditional Statement

A statement that performs different actions based on the truth value of a condition.

Data Type

A classification of data that tells the compiler or interpreter how the programmer intends to use the data.

Static

A keyword that indicates a field or method is shared among all instances of a class.

Final

A keyword used to declare constants or methods that cannot be overridden, or classes that cannot be subclassed.

Enum

A special data type that enables for a variable to be a set of predefined constants.

Annotation

A form of metadata that provides data about a program but is not part of the program itself.

Thread

A thread of execution in a program, allowing for concurrent operations within the program.

Garbage Collection

The process by which Java programs perform automatic memory management.

JVM (Java Virtual Machine)

An abstract machine that enables a computer to run a Java program.

JDK (Java Development Kit)

A software development kit for developing Java applications.

JRE (Java Runtime Environment)

Provides the libraries, the Java Virtual Machine, and other components to run applications written in Java.

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End Notes

In this article, we explored the concepts of Java syntax, starting with its definition and importance in the context of programming. We learned the fundamental syntax rules that govern Java code structure, ensuring clarity and readability. By examining major Java concepts with concise explanations and syntax examples, we provided a practical guide to the language's core elements. Additionally, including basic Java terminologies further enriched the understanding, offering readers a comprehensive overview. This exploration not only serves as an essential resource for beginners but also as a quick reference for experienced programmers, highlighting the elegance and efficiency of Java as a programming language.

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FAQs

What is the basic structure of a Java program?

A Java program typically consists of at least one class and a main method which serves as the entry point of the program. Each class is defined with the class keyword, followed by class name and a set of curly braces containing its members. The main method is declared as public static void main(String[] args). The code inside this method is executed when the program starts.

What are the rules for naming a Java identifier, such as a class, method, or variable?

Java identifiers must begin with a letter (A-Z or a-z), currency character ($), or an underscore (_). Subsequent characters may also be digits (0-9). Java is case-sensitive, which means that myVariable, MyVariable, and MYVARIABLE are different identifiers.

How are comments written in Java and what are their types?

Java supports single-line comments, multi-line comments, and documentation comments. Single-line comments start with // and continue to the end of the line. Multi-line comments are enclosed between /* and */. Documentation comments, used for generating documentation, are enclosed between /** and */.

What is a package in Java and how is it declared?

A package in Java is a namespace that organizes a set of related classes and interfaces. It helps to avoid name conflicts and to write a modular program. Packages are declared at the very beginning of a Java source file using the package keyword followed by the package name.

What are Java access specifiers and what do they do?

Java access specifiers, also known as access modifiers, define the visibility of classes, methods, and variables. There are four types: public, protected, default (no modifier), and private. public means the member is visible to all classes everywhere, protected means it is visible to classes in the same package and subclasses, default means it is visible to classes in the same package, and private means it is visible only within its own class.

About the Author
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Esha Gupta
Associate Senior Executive

Hello, world! I'm Esha Gupta, your go-to Technical Content Developer focusing on Java, Data Structures and Algorithms, and Front End Development. Alongside these specialities, I have a zest for immersing myself in v... Read Full Bio